Multiple endocrine neoplasia type 1 (MEN1) includes varying combinations of more than 20 endocrine and non-endocrine tumors. Endocrine tumors become evident either by overproduction of hormones by the tumor or by growth of the tumor itself. Parathyroid tumors are the most common MEN1-associated endocrinopathy; onset in 90% of individuals is between ages 20 and 25 years with hypercalcemia evident by age 50 years; hypercalcemia causes lethargy, depression, confusion, anorexia, constipation, nausea, vomiting, diuresis, dehydration, hypercalciuria, kidney stones, increased bone resorption/fracture risk, hypertension, and shortened QT interval. Pituitary tumors include prolactinoma (the most common), which manifests as oligomenorrhea/amenorrhea and galactorrhea in females and sexual dysfunction in males. Well-differentiated endocrine tumors of the gastro-entero-pancreatic (GEP) tract can manifest as Zollinger-Ellison syndrome (gastrinoma); hypoglycemia (insulinoma); hyperglycemia, anorexia, glossitis, anemia, diarrhea, venous thrombosis, and skin rash (glucagonoma); and watery diarrhea, hypokalemia, and achlorhydria syndrome (vasoactive intestinal peptide [VIP]-secreting tumor). Carcinoid tumors are non-hormone-secreting and can manifest as a large mass after age 50 years. Adrenocortical tumors can be associated with primary hypercortisolism or hyperaldosteronism. Non-endocrine tumors include facial angiofibromas, collagenomas, lipomas, meningiomas, ependymomas, and leiomyomas.

Marden-Walker syndrome (MWKS) is characterized by psychomotor retardation, a mask-like face with blepharophimosis, micrognathia and a high-arched or cleft palate, low-set ears, kyphoscoliosis, and joint contractures. Other features may include Dandy-Walker malformation with hydrocephalus and vertebral abnormalities (summary by Schrander-Stumpel et al., 1993). There are 2 distal arthrogryposis syndromes with features overlapping those of Marden-Walker syndrome that are also caused by heterozygous mutation in PIEZO2: distal arthrogryposis type 3 (DA3, or Gordon syndrome; 114300) and distal arthrogryposis type 5 (DA5; 108145), which are distinguished by the presence of cleft palate and ocular abnormalities, respectively. McMillin et al. (2014) suggested that the 3 disorders may represent variable expressivity of the same condition.